European red mite, Panonychus ulmi (Koch): European red mite is a major, and one of the most difficult pests to control on apple in West Virginia. Varieties such as Red Delicious and York are especially vulnerable to injury. Moderate to high populations of this foliage-feeding pest can reduce fruit size, and result in the production of fewer and less vigorous fruit buds for the following season. This injury is more severe during periods of drought stress. High populations late in the season can result in the indirect downgrading of fruit by depositing overwintering eggs in the calyx end of fruits.

Chemical control: Acaricide applications to control European red mite are typically targeted at the overwintering egg stage during the prebloom period (2-inch green stage to pink) and/or the motile stages during the postbloom period. In some cases, a single acaricide application during prebloom or at petal fall may provide season-long control. The need for postbloom applications (1 to 2) is determined by monitoring motile stages, and is based on specific action thresholds as a function of crop load (bushels/acre) and time of season.

Amount used

Acaricide

% of acres treated

lb a.i./acre/application

lb a.i./acre/year

Abamectin

18

0.0125

0.0125

Clofentezine

1

0.125

0.125

Formetanate hydrochloride

7

0.69 - 0.92

0.69 - 0.92

Hexythiazox

1

0.09

0.09

Oxamyl

8

0.375 - 0.75

0.375 - 0.75

Petroleum distillate

48

3 - 6 gallons

3 - 6 gallons

Pyridaben

17

0.165

0.165